Physical Science / Unit 1: Science Skills and Measurement
1.4 Graphs and Data
Notes
Graphs show patterns in data.
- A line graph shows how something changes over time or with another variable. A bar graph compares categories. A circle graph shows parts of a whole.
- Put the independent variable on the x-axis and the dependent variable on the y-axis. Label axes with units.
- The slope of a line is rise over run: $\displaystyle \text{slope} = \frac{\Delta y}{\Delta x}$.
- Example: A line passes through $(0, 0)$ and $(4, 20)$. Slope $\displaystyle = \frac{20 - 0}{4 - 0} = 5$.
- A straight line through the origin shows a direct proportion.
Practice
Which type of graph is best for showing how a pond's temperature changes during one day?
A line graph shows change over time.
In an experiment on how fertilizer amount affects plant height, which variable goes on the x-axis?
The independent variable (fertilizer) goes on the x-axis.
On a distance-time graph, a straight line goes from 0 m at 0 s to 40 m at 8 s. What is the slope?
Slope $\displaystyle = \frac{40}{8} = 5$ m/s.
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